It will be appreciated that copolymeric compositions are well known, and further, that literally thousands of such polymers have been disclosed. Additionally, copolymeric compositions are well known where a silicone constitutes a major and essential consitutent. Within the silicone copolymer may be either carbonate identifiable groups or ester identifiable groups.
With regard to the presence of a carbonate group in a polysiloxane copolymer, attention is directed to U.S. Pat. No. 2,999,845 to Eugent P. Goldberg. Simply stated, the compositions of Goldberg comprise dihydric phenol derived groups linked by both carbonate and siloxy groups. With regard to the presence of an ester group in a polysiloxane copolymer, attention is directed to U.S. Pat. No. 3,701,815 to Matzner, et al. The patentees thereof disclose therein a thermoplastic siloxane-polyester block copolymer having siloxane blocks that are linear and contain dihydrocarbyl-siloxane groups and polyester blocks that are linear and contain groups derived from aromatic dicarboxylic acids and aromatic diols.
None of the prior art workers have disclosed the concept of providing a thermoplastic silicone copolymer wherein there is included aromatic carbonate and aromatic ester groups all well defined and present in specific proportions to provide materials which are capable of withstanding heat sterilizing temperatures (at least 100.degree. C.) to permit use in medical equipment, yet which can also be radio frequency dielectrically-sealed, for efficient and convenient manufacturing of flexible films, bags, tubing components, and the like made of the material.
The present invention relates to this concept, i.e. a heat-sterilizable, R.F. dielectric-sealable thermoplastic silicone copolymer, and a method for producing it.
The organic polymer component may be crystalline or amorphous at the temperature of use. Consequently, at the temperature of use, the copolymers are strong plastics which may be rigid or flexible whereas at higher temperatures the copolymer is a viscous liquid which may be fabricated by conventional thermoplastic methods. The constituents in the polymer, as will be seen below, may be combined in different ratios and with varying molecular sizes with respect to the constituents, so as to produce copolymers which have a wide range of mechanical and thermal properties, both at the use temperatures and at the melt fabrication temperatures.